Water ski



Oct 2, 1962 w. P. ABBOTT ETAL 3,056,148

WATER SKI 2 Sheets-Sheet 1 Filed July 5, 1959 @QM NN Oct. 2, 1962 w. P. ABBOTT ETAL 3,056,148

WATER SKI 2 Sheecs--SheeiI 2 Filed July s, 1959 1NVENTOR5 WAM/HM R A5507? ,55AM/TH A. WA4/*J j 7% fraz/Uff! United States Patent O psa 3,656,148 WATER SKI William I. Abbott, Pasadena, and Kenneth A. Waits, lil'odesto, Calif., assignors to W. I. `Voit Rubber Corp., a corporation of California Filed July 3, 1959, Ser. No. 824,845 7 Claims. (Cl. 9-310) This invention relates to water skis and more particularly to the so-ealled slalom water skis. The slalom Skiing is that type of skiing in which only one ski is used for supporting the rider as differentiated from the normal use of two skis in water skiing. Only those obtaining a better than basic knowledge of water skiing are capable of using the so-called slalom ski.

The conventional water skis have a continuous flat bottom surface running the full length of the ski from` the upwardly curved front end to the rear, or aft, end of the ski, the rear end of the ski ending in a `flat rectangular end. At average speed of water skiing approximately 70 to 50% of the rear flat surface of the water ski is in direct contact with water and the resultant force, supporting the rider, its direction, and the point of its application are such that by far the greater weight of the rider is supported by his rear leg rather than his front leg when only one ski is used for skiing. Such weight distribution produces disproportionate tiring of the rear leg and an uncomfortable straining on the calf of the rear leg. Moreover, because of the flat nature of the surface, such ski provides only a limited maneuverability, self-rectifying balance and the concomitant stability.

The invention discloses a water ski which furnishes greater maneuverability, a more uniform weight distribution between the two legs of the rider, and, also, `greater inherent stability which is obtained by providing a V- shaped hull, and, also, by providing an upturned aft plane, this latter plane providing greater lift and decreasing the overall drag of the ski.

It is, therefore, an object of this invention to provide a water ski provided with an upturned aft plane portion for improving stability, maneuverability, lift and decreasing drag, and for obtaining a more uniform weight distribution `between the two legs of the rider.

It is an additional object of this invention to provide a water ski of the above type which also has a Vhull for improving the smoothness of the ride and for providing such ski with a self-rectifying balance.

In accordance with the invention, the water ski is provided with an upturned toe portion, a flat mid-portion and an upturned aft plane portion, the latter constituting approximately 10% of the weight supporting plane of the ski when the latter is in use at low to average speed. This aft plane forms an angle which is not less than 7 and not more than 16 with the front portion of the ski. By providing such upturned aft plane, one obtains two resultant forces acting on the two planes of the ski, the first plane being the front plane, and the second plane being the upturned aft plane. Since these two planes, or these two surfaces, subtend an angle of 165, there is a first resulting force having one `direction determined by the angle of inclination of the first surface with respect to the water and a second force determined by the inclination of the upturned aft plane with respect to the water. The angle between these two reaction forces is a function of the angle between the two planes and also is a function of the speed of the ride. The directions, as well as the magnitudes of these two reaction force vectors are such that they produce a more even distribution of the forces between the two legs of the rider, namely that both legs evenly contribute to the transmission of the resultant force to the ski and, therefore, there is a greater stability of the rider on the ski provided with an aft plane. In the prior skis, having only a single fiat surface, and having no upturned aft plane, as mentioned previously, it is the rear leg that is primarily responsible 4for supporting the rider and for transmitting the resultant force to the ski, while the front leg remains, in the main, idle. When the resultant force thus is transmitted through one point contact (one leg of the rider), the equilibrium of such vectorial relationship of the forces is more precarious as compared to the two counter, or reaction, forces acting upwards and the two direct forces counter balancing them and acting downwards, the two upward forces forming an angle with respect to each other, and the two downward forces also forming a corresponding angle with respect to each other. With such distribution of the force vectors, the equilibrium possesses an inherent self-rectifying characteristic in that if one of the vectors is decreased, then the other vector is automatically increased with the resultant tendency to restore the balance to its equilibrium position. The equilibrium, described above, is in the plane of the force exerted on the skier by the pulling rope.

The stability in the transverse plane is also improved by providing a V-hull construction in which the at surfaces, that are normally in contact With water, are cornposed of four surfaces at an angle with respect to each other. The two `front surfaces, corresponding to the front bottom portion of the ski, are inclined with respect to each other and subtend an angle in the order of and the two aft surfaces, on the upturned aft plane, are also inclined with respect to each other and subtended at an angle of approximately 166. In this manner, when the pressure exerted on one inclined surface is decreased because of the shift in the direction of the `forces `acting on the ski, then the pressure exerted on the complementary, adjacent inclined surface is increased with the result that it also tends to rectify or restore the position of the ski to its normal position, or that position in which the pressures exerted on the two slanted surfaces are equal to each other. This type of V-hull construction produces a better response on turns and it also decreases the drag produced between water and the ski because of the concornitant change in the boundary layer between the water and the ski.

Referring to the drawings:

FIG. 1 is a plane view of a slalom ski with a rectangular aft end.

FIG. 2 is a side View of the same ski.

FIG. 3 is a transverse cross sectional view of the same ski taken along line 3-3 illustrated in FIG. 2.

FIG. 4 illustrates the position of the ski and of the skier in the skiing position.

FIG. 5 is a plain view of another version of the ski having a tapered aft end and a Vhull.

FIG. 6 is a side View of the ski illustrated in FIG. 5.

FIG. 7 is a transverse sectional view of the ski, shown in FIGS. 5 and 6, taken along line 7 7 illustrated in FIG. 6.

FIG. 8 is a transverse sectional View of the ski of FIGS. 5 and 6 taken along line S-S illustrated in FIG. 6.

The shape of the first version of the water ski is illustrated in FIGS. l, 2 and 3. It includes the front upturned toe portion A, the mid portion B and the upturned aft portion C, The body 10 of the ski is made of inlaid mahagony and the toe 11 of the ski is made of laminated mahagony and maple, the laminations being illustrated by line 12 in FIG. 2. The upturned aft portion 0, which is Ialso numbered as portion I4 in FIGS. l land 2, is also of laminated construction, identical to that used in making toe 12 of the ski. The -laminations of the upturned aft portion are illustrated by lines I6 in FIG. 2. The slalom ski is provided with conventional toe and heel assemblies 18 and 20, the heel assembly being provided with an adjustable plate 22 and a knurled stud 24 Iwhich ts into a slot 26 in plate 22. Plate 22 forms a sliding contact with the side bars 28 and 30 of the heel assembly and it is also provided with a ilexible heel 32 made of such materials as neoprene rubber, or any suitable synthetic resin such `as polyvinyl chloride. The position of the heel is adjusted by loosening and tightening slide 24 and sliding the adjustable metallic plate to a desired position. The ski is also provided with a second toe assembly 34 and a friction foot pad 36 also made of neoprene rubber with a knurled surface so as to provide a skid proof base for the second leg of the skier. The upturned aft portion C forms an angle X with a line 37, which represents a continuation of a line 38 defining the bottom surface of the mid portion B of the ski. Therefore, angle X is the angle between lines 37 and 39, line 39 being the longitudinal axis of the upturned aft straight portion C of the ski. Angle X is not an especially critical angle but it has been determined experimentally that with the speeds currently used by the skiers, which is determined by the speeds of the boats used for towing the skiers, this angle should be not less than 7 and not more than 16.

The upturned aft portion is provided with a fin 40 which can be made either of synthetic resin, or zinc which resists corrosion in salt water. The approximate proportions of the 71 slalom ski, illustrated in FIGS. 1 and 2, are as follows: Part A is approximately 14" long, part B is `approximately 40l long and part C is approximately 17 long, or approximately 40% of the length of the mid portion B. Parts C and B merge into each other by means of a gradual smooth curve which interconnects the upturned straight portion C with the straight mid portion 13. The upturned aft portion C, therefore, includes two parts: the upturned curved aft portion and a straight aft portion. The `above mentioned dimensions may be varied to a limited extent (the length of the aft portion may be from 30% to 50% of the length of the mid-portion) and are suitable for a slalom ski for a skier of aver-age weight, such as 100- 190 lbs. when the X angle is in the order of 10 and the ski is 7% wide.

The ski, illustrated -in FIGS. l and 2, has a rectangular cross section 300, illustrated in FIG. 3, which also illustrates the upturned toe 11. The upturned aft plane portion of the ski in FIGS. l, 2 and 3 has a uniform width, equal to the width of the central portion B, and its aft end has =a rectangular end. The bottom surface of the ski is a flat surface.

Referring now to FIGS. and 6, which illustrate the second version of a slalom ski provided with a V-shaped hull and a tapered upturned aft portion, the plan view of this aft end has an outline of a bisected ellipse joined to the aft end of the central portion B of the ski. This semi-elliptic end increases the maneuverability of the skis as compared to the rectangular end shown in FIG. l. The side view of this ski, illustrated in FIG. 6, indicates that the ski is provided with a V-shaped portion 600 which extends from point 601 to the trailing end 602 of the ski. The ski has la flat bottom from point 601 to point 603, l'which is the tip of the upturned toe of the ski. The front portion of the ski has a rectangular cross section 700, .illustrated in FIG. 7 and, therefore, this portion of the ski is identically shaped to the ski illustrated in FIGS. l, 2 and 3. Section 8-8 of this ski is illustrated in FIG. 8 which illustrates the transverse V-shaped section of the ski hull, provided with two inclined surfaces 800 and 801 which subtend an Iangle Y. It is these two inclined surfaces 800 and 801 that form the V-shaped hull of the ski and this V-shaped hull extends frorn point 601 all the way to the aft end of the ski. The ski, illustrated in FIGS. 5, 6, 7 and 8 is also provided with an upturned aft portion C which is identical to the upturned aft portion C in FIG. 2, ex-

4 cept that it has a semi-elliptic outline in plan view. It also forms an angle X between the lines 37 and 39' which, as mentioned previously, is not less than 7 and not more than 16. The ski is also provided with rudder 40 of the type illustrated in FIG. 2.

The V-shaped hull with the surfaces 800 and 801 provides the additional lateral stability to the ski by always presenting either a flat inclined surface 800, or a flat inclined surface 801 to the water, when the position of the ski is shifted for a turn or when the skier follows a zig-zag pass. Such V-shaped bottom, or hull, produces a quicker and easier response on the turns and a greater stability in that the ski With this type of hull does not slide laterally from under the skier when it lis placed into a slanted position with respect to a. horizontal plane during the turns. Because of the inclination of the two surfaces S00 and 801 with respect to each other, if for instance, the ski is rotated counter clockwise in FIG. 8 with respect to the horizontal line 803, the pressure on surface 800 is decreased, while the pressure on surface 801 is increased with the result that a turning couple acts on the ski, which rotates itin a clock-wise direction. This turning couple is produced due to the decrease in the force 806 and the increase in the force 807 diagrammatica-lly illustrated in FIG. 6 by the Vectors S06 and 807 perpendicular to the inclined surfaces S00l and 801. The same turning couple also takes place when the ski is rotated in the clock-wise direction with respect to line S03, except that in this case the turning couple will endeavor to turn the ski in the counter-clock-wise direction so as to restore the position of the ski to its horizontal position illustrated in FIG. 8. It is this creation of the turning couples by the V-hulls that is referred to in this specification `as being a self-rectifying property of the ski in la transverse plane, or in a plane perpendiculanto plane of the pulling force exerted on the ski and the skier by -a tow-rope 400 in FIG. 4.

Referring now to FIG. 4, it illustrates the position of the skier 401 on a slalom ski 402 when he is towed by the tow-rope 400. The forces exerted -by the tow-rope and the skier may be represented by the horizontal force 410 and a vertical force 412, the resultant force acting on the ski being force 414, which forms an angle Z with respect to the vertical force 412. Force 412 will remain constant as long as the same skier is considered and force 410 is a function of the speed of the boat and its towrope, this force gradually increasing with the increase in this speed. The resultant counter force, or the reaction, acting on the ski, obviously should be equal and opposite in direction to the resultant force 414 as long as the skier maintains his equilibrium on the ski. This resultant counter force may be resolved so as to produce the vector triangles including vectors 416, 417 and 41S acting on surface D of the ski and the vectors 419, 420 and 421 acting on the upturned aft plane C of the ski. Vectors 416 and 419 are two horizontal vectors and vectors 41S and 421 are perpendicular to the respective surfaces D and C of the ski. Therefore, these two forces 418 and 421 form an angle a which is equal to angle X in FIG. 2. Such vectorial representation of the reaction forces, acting on the two planes of the ski, indicates that the ski will also have a turning couple approximately at the point of its bend 425 which is produced by the vectors 418, 421. One can very readily see that if vector 421 increases, vector 418 will at once decrease with the result that a counterclockwise turning action will be produced on the ski so as to restore it to the position indicated in FIG. 4. The opposite turning force will act on the ski if the ski is turned counterclockwise. Because of the existence of the two forces 418 .and 421, which form an angle a with respect to each other, the ski has the self-rectifying properties in the plane of the force vectors 410, 412, 414, 416, 421, etc., this self-rectifying action being comparable to that provided by the V-hull. No such self-rectifying action exists in a at ski, having a flat end and having no upturned .aft plane, because in such a ski there is only one vectorial triangle comparable to that illustrated by vectors 416, 417 and 418 Which is not capable of producing two vectors at an angle with respect to each other in the manner illustrated in FIG. 4. In the flat skis known to the prior art, with the straight aft portion, the resultant vector acting on the ski which is equal and opposite in direction to vector 414 passes primarily through that portion of the ski which is directly under the rear leg of the user with the result that, as mentioned in the introductory part of the specification, the rear leg of the skier is the one which provides by far the greatest part of the support, while the front leg plays only a minor role. This is not so in the case of the ski having an upturned aft plane because this plane has a tendency to shift the resultant counter force into the position half way between the legs 4and it also changes its direction so that the weight of the ski is uniformly distributed between the two legs.

It should be also noted here that since the ski with the upturned att plane olers a lower resistance than the at ski, vector 410 in this case will be smaller than it is the case in connection with the flat ski, and, therefore, angle Z will be smaller in this case than with the flat ski. Therefore, there is not only a readjustment of the magnitude in the vectorial relationship but also a readjustment between their angular relationships which contribute to the stability of the rider and produce a more uniform weight distribution between the two legs. This, in turn, contributes to the maneuverability and the ease of control and handling of the ski by the rider.

What is claimed as new is:

1. A water ski having three portions, an upturned toe portion, a straight mid-portion and an upturned aft portion including an upturned curved aft portion and a straight aft portion with a stationary lin attached to the end of said straight aft portion, the first mentioned aft portion having a length in the order of 40% the length of said mid-portion, whereby the tirst mentioned aft portion produces a significant part of the lift of said ski along the water line when said ski is in use, said upturned curved aft portion forming a smooth junction with the mid-portion of the ski, the first mentioned upturned aft portion comprising the dominant portion for supporting a skier when said water ski is travelling at high speed.

2. The structure of claim 1 wherein the first mentioned upturned aft portion forms an angle with said mid portion which is in the order of from 7 to 16.

3. The water ski as dened in claim 1 wherein said ski is also provided with a V-hull, said V-hull extending through the greater portion of the mid-portion of the ski and through the entire upturned aft portion of the ski.

4. The water ski as defined in claim 3 wherein said ski also includes one complete heel and toe assembly centrally positioned at the mid-portion of the ski, and a toe assembly positioned at the aft end of the mid-portion of the ski.

5. A slalom Water ski having an upturned toe, a straight mid portion, said toe merging into said straight mid portion by means of a continuous curve, and an upturned ,aft portion, said aft portion including a curved aft portion and a straight aft portion, said straight mid portion merging into said curved aft portion, said straight aft portion forming an angle in the order of from 7 t0 16 with said straight mid portion.

6. The ski as delined in claim 5 in which said upturned aft portion has a substantially semi-elliptic plan view, and a V-hull extending through the greater portion of the straight mid portion and through the entire upturned aft portion of said ski.

7. A slalom water ski having `a toe portion, a midportion having a pair of foot-receiving members disposed in tandem thereon, said mid-portion being adapted to provide a first lift force during ski operation, and an aft portion disposed rearward of the rearwardmost one of said foot-receiving members for providing a significant auxiliary lift force during ski operation, said aft portion including an upturned curved aft portion, forming a continuation of said mid-portion, and `a straight aft portion forming a continuation of said curved aft portion, said straight aft portion being inclined angularly upward to the extended plane of said mid-portion, the rst mentioned aft portion constituting from 30% to 50% of the length of said mid-portion.

References Cited in the tile of this patent UNITED STATES PATENTS 1,719,059 Krupka et al Iuly 2, 1929 1,832,862 Grumman Nov. 24, 1931 2,494,316 Sanderson Jan. 10, 1950 2,716,246 Billingham Aug. 30, 1955 FOREIGN PATENTS 376,861 Italy Dec. 29, 1939 945,210 France Apr. 28, 1949 821,162 Germany Nov. 15, 1951 OTHER REFERENCES A publication called: Kimball Water Skis; Kimball Mfg. Corp., 1270 Penna. Ave., San Francisco 7, Calif., Publ. No. DA 2-27 8-56. 

